JP6477510B2 - Control device for automatic transmission - Google Patents

Description

  The present invention relates to a control device for an automatic transmission including a plurality of friction engagement elements, and more particularly to a control device for an automatic transmission that performs a learning operation of a torque transmission start point when the vehicle is stopped.

  2. Description of the Related Art Conventionally, for example, in a vehicle equipped with a starting clutch or a stepped transmission, neutral control is performed while driving a power source. In the neutral control, for example, when the shift position of the automatic transmission is the forward travel position (for example, D position) while the vehicle is stopped, and a predetermined condition is satisfied, the start clutch or the step speed of the stepped transmission is In this control, the frictional engagement element (hereinafter referred to as “starting clutch”) that forms the forward gear is switched from engagement to release to interrupt torque transmission. As a result, the load on the internal combustion engine is reduced and the fuel consumption while the vehicle is stopped is suppressed. Thereafter, when the driver steps on the accelerator, the starting clutch is engaged again, the automatic transmission forms a forward gear, and the vehicle moves forward.

  To achieve neutral control, it is important to accurately know the torque transmission start pressure or torque transmission start point at which the starting clutch begins to have a torque capacity that can be transmitted in order to perform a smooth start with less shock. . Therefore, a clutch control device that learns the torque transmission start pressure of the starting clutch when neutral control is started while the power source is driven is known (for example, Patent Document 1). In the clutch control device described in Patent Document 1, for example, the torque transmission start point of the starting clutch is learned based on the change in the rotational speed of the rotating element of the automatic transmission caused by changing the starting clutch from the engaged state to the released state. To do.

  Further, when the neutral control is being executed, the friction clutch for setting the standby hydraulic pressure after precharging that rapidly fills the friction engagement element with the hydraulic oil in the play area of the first half of the stroke of the clutch piston is set. Known is an automatic transmission that learns when the difference value between the turbine rotational speed and the engine rotational speed when the hydraulic pressure is gradually decreased to a predetermined value or less as a torque transmission start pressure, and a standby hydraulic pressure value setting method for the automatic transmission. (For example, refer to Patent Document 2).

  Furthermore, while the vehicle is stopped, after disconnecting the starting clutch provided between the fluid coupling fastened behind the engine and the transmission, the connection amount (hydraulic pressure) of the starting clutch is gradually increased, A vehicle power transmission device that calculates a torque transmission amount from a speed ratio of rotating elements arranged before and after the starting clutch, and learns a clutch connection amount at which the calculated torque transmission amount reaches a predetermined value as a torque transmission start point (See, for example, Patent Document 3).

  Further, a guard method at the time of setting a hydraulic characteristic value for learning, as a precharge pressure, a standby hydraulic pressure based on a change in turbine rotational speed when the hydraulic pressure supplied to the friction engagement element is gradually increased or decreased while the vehicle is stopped, and for the same A control device is known (see, for example, Patent Document 4).

  Furthermore, for the purpose of catching the engagement start point where torque capacity starts to be generated, the learning target clutch is released, the output shaft of the automatic transmission is fixed (stopped), and the input rotational speed is kept constant. Thus, the automatic transmission characteristic correction system for increasing the hydraulic pressure to the released engagement element and learning the reference hydraulic pressure from the hydraulic control amount at the time when the speed ratio between the turbine rotation speed and the input shaft rotation speed becomes a predetermined value or less is provided. It is known (see, for example, Patent Document 5).

JP 2014-77486 A JP 2008-106943 A JP 2008-82528 A JP 2005-233369 A JP 2010-48401 A

  However, when learning is being performed during neutral control, for example, when the start condition is satisfied by, for example, depressing the accelerator pedal while the engagement pressure of the start clutch is being lowered, the start clutch is slightly Due to the engaged stage, it may take time to transmit the torque to the drive wheels by performing slip engagement in order to start the vehicle smoothly.

  The present invention has been made paying attention to the technical problem described above, and allows a stopped vehicle to start smoothly and quickly when a start condition is satisfied during learning of an engagement pressure of a friction engagement element. It is an object of the present invention to provide a control device for an automatic transmission that can perform the above.

  In order to achieve the above object, according to the present invention, a plurality of friction engagement elements that are arranged between a power source and a drive wheel and can change torque capacity by supplying hydraulic pressure, and the friction engagement A control unit for controlling the supply of the hydraulic pressure to change each of the combined elements to an engaged state or a released state, wherein the control unit rotates the driving wheel. When the starting condition of the plurality of frictional engagement elements is satisfied, the frictional force other than the first frictional engagement element that generates the torque capacity and transmits torque to the drive wheels when the starting condition among the plurality of frictional engagement elements is satisfied. Differential rotation between the input side and the output side of the first friction engagement element, which is caused by changing the combination element to the release state and changing the first friction engagement element from the engagement state to the release state, or Changes according to the differential rotation A learning unit that learns a torque transmission start point of the first friction engagement element based on a change in the rotation element, and the learning unit is performing the learning and the start condition is satisfied, Drive torque transmitted to the drive wheel by bringing the first friction engagement element into the engaged state and gradually changing the second friction engagement element other than the first friction engagement element into the engaged state. It is characterized by being comprised so that it may raise.

  According to the present invention, when the start condition is established during learning that is performed while changing the first friction engagement element from the engagement state to the release state, the first friction engagement element is set to the engagement state. The second frictional engagement element is gradually engaged. As a result, the driving torque transmitted to the driving wheels can be increased, so that the vehicle that is stopped during learning can be started smoothly and quickly.

It is explanatory drawing which shows an example of the vehicle to which this invention is applied. It is a skeleton figure which shows an example of the automatic transmission of the vehicle demonstrated in FIG. 3 is an operation chart showing the operation of the friction engagement element of the automatic transmission described in FIG. 2. It is a collinear diagram which shows the operation state of the 1-speed gear stage of an automatic transmission. It is a circuit diagram which shows the principal part of the hydraulic control circuit which supplies hydraulic pressure to a friction engagement element. It is a collinear diagram which shows the 2nd transmission part of the state which engaged the 1st clutch at the time of learning. It is a collinear diagram which shows the 2nd transmission part of the state which released the 1st clutch at the time of learning. It is explanatory drawing which shows the relationship between the hydraulic pressure of a 1st clutch, and intermediate | middle rotational speed Nm. It is a flowchart explaining the operation | movement procedure of ECU containing a learning part. It is an alignment chart which shows the state which engaged the 2nd brake. It is a flowchart which shows another example which added AT oil temperature to the conditions of learning. It is a graph which shows the relationship between drag torque and AT oil temperature.

  Hereinafter, embodiments will be described with reference to the drawings. FIG. 1 shows an example of a vehicle 10 to which the present invention is applied. The vehicle 10 includes an engine 11, an automatic transmission (A / T) 13, an output shaft 14, a differential 15, a drive shaft 16, a pair of drive wheels 17, 18 and the like. The engine 11 outputs drive torque by burning the air-fuel mixture supplied to the cylinder. The drive torque output from the engine 11 is input to the input shaft 19 of the automatic transmission 13 and transmitted from the output shaft 14 of the automatic transmission 13 to the left and right drive wheels 17 and 18 via the differential 15 and the drive shaft 16. Is done. The engine 11 is an example of a power source. Further, although the drive wheels 17 and 18 are rear wheels, they may be front wheels.

  A throttle valve 20 is provided in the intake path of the engine 11. The throttle valve 20 can be adjusted in throttle opening degree Ta by a drive motor 21. The throttle opening degree Ta is detected by a throttle opening degree sensor 22. The detected throttle opening information is input to an ECU (Electronic Control Unit) 23. The ECU 23 inputs a detection signal from an accelerator opening sensor 25 that detects an accelerator opening θTH that is an operation amount of the accelerator pedal 24. The ECU 23 performs a calculation based on various signals and various data to calculate a target throttle opening, and controls the drive motor 21 based on the target throttle opening to adjust the operating state of the engine 11.

  The ECU 23 receives signals from an engine speed sensor 27 that detects an engine speed Ne that is an actual speed of the crankshaft of the engine 11 and an output speed sensor 28 that detects an output speed No of the automatic transmission 13. doing. The ECU 23 also receives a signal from an input rotation speed sensor 29 that detects the input rotation speed Nin of the automatic transmission 13. Further, the ECU 23 receives a signal from an intermediate rotational speed sensor 30 that detects the rotational speed (hereinafter referred to as “intermediate rotational speed”) Nm of the intermediate rotational element of the automatic transmission 13. Furthermore, the ECU 23 receives a signal from a temperature sensor 31 that detects the temperature (oil temperature) of oil (ATF: Automatic Transmission Fluid) used for the operation and lubrication of the automatic transmission 13.

  The ECU 23 calculates the vehicle speed V based on the information of the output rotational speed No obtained from the output rotational speed sensor 28, and calculates the accelerator opening degree θTH based on the detection signal of the throttle opening degree Ta obtained from the throttle opening degree sensor 22. calculate. The ECU 23 calculates a target gear position in the automatic transmission 13 with reference to the shift map based on the calculated vehicle speed V and the accelerator opening θTH. The shift map is represented by an operation region having the vehicle speed V and the accelerator opening θTH as the horizontal axis and the vertical axis, and is stored in advance in the ROM 32 used by the ECU 23. Then, the ECU 23 controls the automatic transmission 13 so that the shift stage of the automatic transmission 13 is set to the target shift stage.

  FIG. 2 is a skeleton diagram showing an example of the automatic transmission of the vehicle described in FIG. As shown in FIG. 2, the automatic transmission 13 includes a double pinion type first planetary gear mechanism 37 in a transmission case (hereinafter referred to as “case”) 36 as a non-rotating member attached to the vehicle 10. The 1st transmission part 38 comprised as a main body is provided. In addition, the case 36 includes a second transmission unit 41 mainly composed of a single pinion type second planetary gear mechanism 39 and a double pinion type third planetary gear mechanism 40. The first transmission unit 38 and the second transmission unit 41 are provided on a common axis, and the rotation of the input shaft 19 is shifted and output from the output shaft 14.

  The path for transmitting the rotation of the input shaft 19 to the second transmission unit 41 at the same speed is the first intermediate output path 42 for transmitting the rotation at a predetermined fixed gear ratio (for example, “= 1.0”). It has become. The first intermediate output path 42 includes a direct connection path 43 that transmits rotation from the input shaft 19 to the second transmission unit 41 without passing through the first planetary gear mechanism 37, and the first intermediate gear path 37 of the first planetary gear mechanism 37. There is an indirect path 44 through which rotation is transmitted to the second transmission unit 41 via one carrier CA1. Further, the transmission path from the input shaft 19 to the second transmission 41 via the first pinion gear P1 and the first ring gear R1 constituting the first carrier CA1 is larger than the first intermediate output path 42 (for example, This is a second intermediate output path 45 that transmits the rotation of the input shaft 19 by shifting (decelerating) at “> 1.0”).

  The second intermediate output path 45 is provided with a first clutch C1 that connects the first ring gear R1 of the first planetary gear mechanism 37 and the third sun gear S3 of the third planetary gear mechanism 40. The first clutch C1 is a hydraulic friction engagement element whose state is switched between an engaged state and a released state by supplying hydraulic pressure, for example. The first clutch C1 is an example of a first friction engagement element. When the first clutch C1 is engaged when the vehicle 10 starts from a stop state, the first clutch C1 forms a second intermediate output path 45 to transmit the driving torque transmitted from the input shaft 19 to the second transmission unit. The signal is transmitted to the output shaft 14 via 41. On the other hand, when the first clutch C1 is released, the second intermediate output path 45 is shut off.

  The automatic transmission 13 includes a second clutch C2, a third clutch C3, a fourth clutch C4, a fourth clutch C4, a friction engagement element for establishing a plurality of gear speeds having different gear ratios, in addition to the first clutch C1 described above. 1 brake B1 and 2nd brake B2 are provided. The second clutch C2, the third clutch C3, the fourth clutch C4, the first brake B1, and the second brake B2 are examples of a hydraulic friction engagement element that can change the torque capacity by supplying hydraulic pressure, for example. .

  The first planetary gear mechanism 37 includes a first sun gear S1, a pair of first pinion gears P1, a first carrier CA1, and a first ring gear R1. Each first pinion gear P1 meshes with the first sun gear S1 and the first ring gear R1. The first carrier CA1 supports the first pinion gear P1 so that it can revolve and rotate. The first sun gear S1 is fixed to the case 36 so as not to rotate. The first carrier CA1 is connected to the input shaft 19.

  The second transmission unit 41 is a Ravigneaux type planetary gear mechanism including a second planetary gear mechanism 39 and a third planetary gear mechanism 40. The second planetary gear mechanism 39 includes a second sun gear S2, a second pinion gear P2, a rear carrier RCA, a rear ring gear RR, a third sun gear S3, and a third pinion gear P3. Second pinion gear P2 meshes with second sun gear S2, rear ring gear RR, and third pinion gear P3. The third pinion gear P3 meshes with the third sun gear S3 of the third planetary gear mechanism 40 in addition to the second pinion gear P2. The rear carrier RCA supports the second pinion gear P2 and the third pinion gear P3 of the third planetary gear mechanism 40 so that they can revolve and rotate. The rear ring gear RR is connected to the output shaft 14.

  The second planetary gear mechanism 39 and the third planetary gear mechanism 40 constitute a first rotation element 48 to a fourth rotation element 51 by being partially connected to each other. The first rotation element 48 constitutes an intermediate rotation element that connects the first transmission unit 38 and the second sun gear S <b> 2 of the second planetary gear mechanism 39. The rotation of the first rotating element 48 is stopped by being connected to the case 36 by the first brake B1. The first rotating element 48 is selectively connected to the first ring gear R1 (second intermediate output path 45) of the first planetary gear mechanism 37 via the third clutch C3. Further, the first rotating element 48 is selectively coupled to the first carrier CA1 (indirect path 44) of the first planetary gear mechanism 37 via the fourth clutch C4.

  The second rotating element 49 (rear carrier RCA) is selectively coupled to the case 36 via the second brake B2, and is selectively coupled to the input shaft 19 (direct coupling path 43) via the second clutch C2. The The third rotating element 50 (rearing gear RR) is integrally connected to the output shaft 14 to output rotation. The fourth rotation element 51 (third sun gear S3) is selectively coupled to the first ring gear R1 via the first clutch C1.

  FIG. 3 is an operation table showing the operation of the friction engagement element of the automatic transmission described in FIG. As shown in FIG. 3, by independently operating a plurality of friction engagement elements in the combinations shown in the operation table, the forward 1st to 8th gears and the reverse 1st and 2nd reverse gears are provided. A step is formed. The first forward speed (1st) is established by engagement of the first clutch C1. That is, the first clutch C <b> 1 constitutes a friction engagement element for transmitting the drive torque generated by the engine 11 to the output shaft 14. At the first forward speed (1st), the second brake B2 is engaged in addition to the first clutch C1. The second brake B2 is a friction engagement element that does not transmit the drive torque generated by the engine 11 to the output shaft 14 alone. The second brake B2 is an example of a second friction engagement element. When all the friction engagement elements are released, parking (P) is established. Thereby, the power transmission from the input shaft 19 to the output shaft 14 is interrupted.

  FIG. 4 is a collinear diagram showing the operating state of the first gear of the automatic transmission. As shown in FIG. 4, the horizontal line 52 described as “0” indicates that the rotational speed (the number of rotations) is zero, and the horizontal line 53 described as “Ne, Nin” above the horizontal line 52 indicates the rotational speed “ 1.0 ", that is, a line indicating the same rotational speed as the input shaft 19. “Ne” represents the engine speed, and “Nin” represents the input speed. Further, each vertical line of the first transmission unit 38 represents the first sun gear S1, the first ring gear R1, and the first carrier CA1 in order from the left side, and the distance therebetween is the gear ratio of the first planetary gear mechanism 37. It is determined according to ρ1. The gear ratio ρ1 is the number of teeth of the first sun gear S1 / the number of teeth of the first ring gear R1. The four vertical lines of the second transmission unit 41 are, in order from the left, the first vertical line is the second sun gear S2 (first rotating element 48), and the second vertical line is the rear carrier RCA (second rotating element 49). Represent. The third vertical line from the left represents the rear ring gear RR (third rotation element 50), and the fourth vertical line represents the third sun gear S3 (fourth rotation element 51). The interval between the four vertical lines of the second transmission unit 41 is determined according to the gear ratio ρ2 of the second planetary gear mechanism 39 and the gear ratio ρ3 of the third planetary gear mechanism 40.

  When both the first clutch C1 and the second brake B2 are engaged together, the first forward speed (1st) at which the maximum speed ratio (the rotational speed of the input shaft 19 / the rotational speed of the output shaft 14) is achieved. Is established. In this case, the fourth rotation element 51 is rotated at a reduced speed with respect to the input shaft 19 via the first transmission unit 38. Further, since the rotation of the second rotating element 49 is stopped by the engagement of the first clutch C1 and the second brake B2, the third rotating element 50 connected to the output shaft 14 is connected to the vertical axis of the rear ring gear RR. It is rotated at a rotational speed 55 represented by an intersection 54 with the straight line 56.

  FIG. 5 is a circuit diagram showing a main part of a hydraulic control circuit that supplies hydraulic pressure to the friction engagement element. As shown in FIG. 5, the vehicle 10 includes a hydraulic control circuit 57 that is comprehensively controlled by the ECU 23. The hydraulic control circuit 57 includes a mechanical oil pump that is rotationally driven by the engine 11, a regulator valve that regulates the line hydraulic pressure PL, and the like, and controls the line hydraulic pressure PL according to the engine load and the like. The hydraulic pressure from the hydraulic actuator (hydraulic cylinder) 58 is applied to the first clutch C1, the hydraulic pressure from the hydraulic actuator 59 to the second clutch C2, the hydraulic pressure from the hydraulic actuator 60 to the third clutch C3, and the hydraulic pressure to the fourth clutch C4. Hydraulic pressure is supplied from the actuator 61. The first brake B1 is supplied with hydraulic pressure from the hydraulic actuator 62, and the second brake B2 is supplied with hydraulic pressure from the hydraulic actuator 63. The hydraulic actuators 58 to 63 are supplied with the line hydraulic pressure PL output from the hydraulic control circuit 57 after being regulated by the linear solenoid valves SL1 to SL6, respectively. Each of the linear solenoid valves SL1 to SL6 adjusts the hydraulic pressure supplied from the hydraulic actuators 58 to 63 by switching control to solenoid excitation or non-excitation state or current control based on a command value from the ECU 23. Hereinafter, the actuators including the hydraulic actuators 58 to 63 are referred to as actuators.

  At the time of start, the ECU 23 gradually changes the amount of connection of the friction engagement elements in order to avoid a shock or engine stall due to sudden torque transmission. For example, when starting the vehicle 10 from the stop state, the ECU 23 controls the control amount of the actuator so as to gradually increase the torque capacity of the friction engagement element. The friction engagement elements are gradually rotated from the slip engagement state in which the clutch is in a half-clutch state, and the rotational speed of the input-side rotation element disposed on the upstream side in the power transmission direction and the output-side rotation element disposed on the downstream side. When the rotation speeds coincide with each other, the slipping amount becomes zero and a complete engagement is achieved.

  By the way, in the friction engagement element, there is an individual difference in the torque capacity at which the half-clutch state is started, and the torque capacity at which the half-clutch state is started changes due to the secular change. Accordingly, the ECU 23 periodically learns the hydraulic pressure value at the half clutch start point, that is, the torque transmission start point at which torque transmission is started, for example, the control amount of the actuator having the torque capacity at which substantial torque transmission starts. It has. The hydraulic control circuit 57 and the ECU 23 are examples of a control unit.

  When the engine 11 is being driven and the vehicle 10 is stopped (the rotation of the drive wheels 17 and 18 is stopped), the learning unit 64 changes all of the friction engagement elements to the released state, and then The control amount of the hydraulic actuator 58 when the clutch C1 is changed to the engaged state and then the first clutch C1 is changed from the engaged state to the released state is learned and corrected. That is, the learning unit 64 decreases the torque capacity with respect to the engaged first clutch C1, determines the torque transmission start point based on the intermediate rotational speed Nm, and at the determined torque transmission start point. For example, the control amount output to the actuator is stored in the RAM 65 and updated.

  FIG. 6 is a collinear diagram showing the second transmission unit in a state in which the first clutch is engaged during learning. In the operation state of FIG. 6, the friction engagement elements other than the first clutch C1 are in the released state. The collinear chart shown in FIG. 6 is a horizontal axis showing the relationship between the gear ratios ρ2 and ρ3 of the second planetary gear mechanism 39 and the third planetary gear mechanism 40 of the second transmission unit 41 and a vertical axis showing a relative rotational speed. It is a two-dimensional coordinate consisting of an axis. The lowermost horizontal line 66 of the three horizontal lines indicates the rotational speed “zero”, and the uppermost horizontal line 53 indicates the rotational speed “1.0”, that is, the engine rotational speed Ne.

  Further, the four vertical lines of the second transmission unit 41 correspond to the second sun gear S2 corresponding to the first rotation element 48, the rear carrier RCA corresponding to the second rotation element 49, and the third rotation element 50 in order from the left. The rear ring gear RR and the third sun gear S3 corresponding to the fourth rotating element 51 are shown. The intervals between the four vertical lines of the second transmission unit 41 are determined according to the gear ratio ρ2 of the second planetary gear mechanism 39 and the gear ratio ρ3 of the third planetary gear mechanism 40, respectively. The gear ratio ρ2 is the ratio of the number of teeth of the second sun gear S2 to the number of teeth of the rear ring gear RR, and the gear ratio ρ3 is the ratio of the number of teeth of the third sun gear S3 to the number of teeth of the rear ring gear RR.

  As shown in FIG. 6, since the vehicle 10 is in a stopped state, the second transmission unit 41 rotates the rear ring gear RR as represented by an intersection 68 where the vertical axis of the rear ring gear RR and the straight line 67 intersect. The number, that is, the output rotation speed No is zero (the rotation of the drive wheels 17 and 18 is zero). This state includes, for example, a state in which any one of the conditions of stop of the vehicle 10, parking brake operation, foot brake operation, and gear-in of the automatic transmission 13 is established. When the first clutch C1 is in the engaged state in this state, the third sun gear S3 generates the friction torque of the first clutch C1 as shown at the intersection 69 between the vertical axis of the third sun gear S3 and the straight line 67. Receiving and rotating in the positive direction. In this case, as shown at the intersection 70 between the vertical axis of the rear carrier RCA and the straight line 67, the rear carrier RCA receives the drag torque of the second clutch C2 and the second brake B2 and rotates in the negative direction. Yes. Furthermore, in this case, as shown at the intersection 71 between the vertical axis of the second sun gear S2 and the straight line 67, the first brake B1, the third clutch C3, and the fourth clutch C4 receive the drag torques respectively. 2 The sun gear S2 is rotating in the negative direction. The rotation speed of the second sun gear S <b> 2 is the same as the intermediate rotation speed Nm of the first rotation element 48.

  FIG. 7 is a collinear diagram showing the second transmission unit in a state in which the first clutch is released during learning. As shown in FIG. 7, the intermediate rotational speed Nm of the first rotating element 48 is changed on the vertical axis of the second sun gear S2 by changing the state of the first clutch C1 from the engaged state to the released state during learning. The rotational speed represented by the intersection 71 with the straight line (dotted line) 67 decreases to the rotational speed represented by the intersection 73 with the straight line (solid line) 72. The first rotating element 48 is an example of a rotating element that changes in accordance with the differential rotation between the input side and the output side of the first friction engagement element.

  FIG. 8 is an explanatory diagram showing the relationship between the hydraulic pressure of the first clutch and the intermediate rotational speed Nm. As shown in FIG. 8, the learning unit 64 monitors the intermediate rotational speed Nm of the first rotating element 48 while decreasing the engagement pressure of the first clutch C1, for example, stepwise, and the intermediate rotational speed Nm is the first rotational speed. It is determined that the engagement pressure when the threshold value (Nmlrn) or less is the half-clutch start pressure, that is, the torque transmission start point. The first threshold (Nmlrn) is determined in advance based on experiments, simulations, and the like.

  FIG. 9 is a flowchart for explaining an operation procedure of the ECU including the learning unit. As shown in FIG. 9, in step S1, it is determined whether the vehicle 10 is stopped. This determination condition includes, for example, any of the following conditions: stop of the vehicle 10, parking brake operation, foot brake operation, and gear-in of the automatic transmission 13. Then, in addition to the above conditions being satisfied, it may be determined whether the rotation speed of the output shaft 14 is zero.

  If the determination is affirmative (Y side), the process proceeds to step S2. In step S2, the state of the friction engagement element of the automatic transmission 13 is changed to the released state. In step S2, if a torque converter is provided, the lockup clutch is engaged and the input shaft 19 is directly connected to the engine 11. In step S3, the first clutch C1 is changed to the engaged state. At this time, the second transmission unit 41 rotates at the rotational speed at which the intermediate rotational speed Nm is represented by the intersection 71 by the operation state described with reference to FIG.

  In step S4, the intermediate speed Nm is monitored while changing the state of the first clutch C1 from the engaged state to the released state. In step S5, it is determined whether the intermediate rotational speed Nm is equal to or less than the first threshold value (Nmlrn). If negative (N side) in step S5, the process proceeds to step S6. In step S6, for example, it is determined whether an engine output increase request including an accelerator opening and an increase in throttle opening due to depression of the accelerator pedal, that is, a start condition is satisfied. If the determination is affirmative (Y side) in step S6, the process proceeds to step S7. In step S7, the first clutch C1 is changed to the engaged state, and the process proceeds to step S8. In step S8, the second brake B2 is gradually changed to the engaged state. That is, the second brake B2 is slip-engaged. By engaging the second clutch B2 with the first clutch C1 engaged, the rotational speed of the rear ring gear RR, that is, the output rotational speed No can be increased. As a result, the vehicle 10 can be started smoothly and quickly by slip engagement from a lower engine rotation speed region.

  If the determination is affirmative (Y side) in step S5, the process proceeds to step S9. In step S9, the learning value is stored, that is, the control value of the actuator that controls the engagement pressure of the first clutch C1 when it is determined that the intermediate rotational speed Nm is equal to or less than the first threshold value (Nmlrn) is stored. If the determination in step S6 is negative (N side), the process proceeds to step S5, and the determination whether the intermediate rotational speed Nm is equal to or less than the first threshold value (Nmlrn) is continued.

  FIG. 10 is an alignment chart showing a state in which the second brake is engaged. As shown in FIG. 10, the operating state of the second transmission unit 41 in a state where the first clutch C1 is changed to the released state during learning, that is, the second transmission unit when the process of step S4 described in FIG. 9 is executed. The operation state 41 is indicated by a one-dot chain line 75. In this state, the rotation of the output shaft 14, that is, the rear ring gear RR is fixed by the weight of the vehicle 10, and the rear carrier RCA and the second sun gear S2 are rotated by the drag torque of the friction engagement element to Balanced. Thereafter, the operation state when the first clutch C1 is changed to the engaged state, that is, the operation state of the second transmission unit 41 when the process of step S7 described in FIG. At this time, the friction torque due to the engagement of the first clutch C1 is acting on the right side of the dotted line 76 with respect to the intersection 68 where the weight load of the vehicle 10 is acting, but the reaction force is on the left side of the dotted line 76. Since it does not act, the rotation speed of the rear ring gear RR, that is, the output rotation speed No is substantially zero.

  A straight line (solid line) 77 indicates the operating state when the second brake B2 is gradually engaged while maintaining the engaged state of the first clutch C1, that is, the first state when the process of step S8 described in FIG. 9 is executed. The operation state of the two-speed change part 41 is represented. In this state, a reaction force acts on the left side of the dotted line 76 with respect to the intersection 68 by the slip engagement of the second brake B2. For this reason, the rotation speed represented by the intersection 78 between the vertical axis and the straight line (solid line) 77 of the rear ring gear RR, that is, the output rotation speed No, increases as compared with the released state (the state of the dotted line 76). That is, for example, when the accelerator pedal is depressed during learning while the vehicle 10 is stopped, the output shaft 14 is driven by maintaining the engagement of the first clutch C1 and gradually engaging the second brake B2. Torque can be increased smoothly and quickly. For this reason, the stopped vehicle 10 can be started smoothly and quickly.

  Incidentally, when the friction engagement element has, for example, a multi-plate clutch structure, low viscosity oil (ATF) may remain in the gap between the clutch plates. In this case, for example, an event (sticking event) in which the clutch plate is dragged by another adjacent clutch plate at a low temperature may occur. That is, in a clutch having a multi-plate clutch structure, the clutch plates are stuck together by low-temperature oil intervening in the groove portions (clutch grooves) of the clutch plates. As a result, for example, when learning is performed in an environment immediately after the engine is started, that is, in a state where the oil is at a low temperature, a large frictional force (friction) is generated in the clutch plate, so that the drag torque is increased and torque transmission is performed. There is a problem that the control value of the actuator as the starting point varies greatly.

  Therefore, in another embodiment shown in FIG. 11, the ECU 23 including the learning unit 64 monitors the AT oil temperature, and performs the learning when the AT oil temperature is equal to or higher than the second threshold (Templrn). FIG. 11 is a flowchart illustrating another example of the operation procedure learned by the ECU 23 including the learning unit 64. As shown in FIG. 11, in step S10, it is determined whether the AT oil temperature is equal to or higher than the second threshold (Templrn) when the vehicle is stopped. And in negative (N side), it transfers to step S1, without implementing learning. In the case of affirmation (Y side), that is, when the AT oil temperature is equal to or higher than the second threshold value (Templrn), learning is performed. The AT oil temperature is monitored based on information obtained from the temperature sensor 31 described with reference to FIG. In FIG. 11, the same or similar procedure as the operation procedure described in FIG. 9 is denoted by the same reference numeral, and detailed description thereof is omitted here.

  FIG. 12 is a graph showing the relationship between drag torque and AT oil temperature. It has been found that the drag torque is generated based on both the input / output rotational speed difference (differential rotation) of the friction engagement element and the AT oil temperature. As shown in FIG. 12, as the AT oil temperature decreases, the viscosity of the oil increases and the drag torque increases. In order to suppress the error range, it is desirable that learning be performed in a region where the rate of change in drag torque is small, that is, in a low region where the drag torque is less than or equal to a predetermined drag torque T1. That is, compared to when the AT oil temperature is equal to or higher than the second threshold value (Templrn), the torque transmission start point is greatly changed, and the relationship between the intermediate rotational speed Nm and the first threshold value (Nmlrn) is not established. In this case, engine stall may occur due to insufficient drive torque or excessive torque capacity when starting. Therefore, in this embodiment, a condition for performing learning is added when the AT oil temperature is equal to or higher than the second threshold (Templrn). The second threshold (Templrn) is determined in advance based on experiments, simulations, or the like so as to be a learning execution region where a stable drag torque can be obtained.

  The present invention is not limited to the specific examples described above. For example, the power source may be an internal combustion engine such as an engine or an internal combustion engine and a generator. Further, the vehicle may be a vehicle provided with a torque converter. Further, the clutch used at the time of learning is not limited to the first clutch C <b> 1 that constitutes the first forward speed gear stage, and may be any frictional engagement element that constitutes the gear stage of the automatic transmission 13. Furthermore, the second friction engagement element is not limited to the second brake B2 as long as it is a friction engagement element that can be engaged with the clutch engaged during learning. Further, the second friction engagement element is not limited to one friction engagement element, and may be a plurality of friction engagement elements.

  Further, in the above-described embodiment, the torque transmission start point that is executed at the time of learning is determined based on the first rotation in which the number of rotations varies depending on the friction torque of the first clutch C1 and the drag torque of the friction engagement elements other than the first clutch C1. This is based on the intermediate rotational speed Nm of the element 48. Instead of this, for example, the rotation may be performed based on the differential rotation between the input side and the output side of the first clutch C1.

  DESCRIPTION OF SYMBOLS 11 ... Engine, 13 ... Automatic transmission, 17, 18 ... Drive wheel, C1 ... 1st clutch, B2 ... 2nd brake, 23 ... ECU, 64 ... Learning part.

Claims (1)

A plurality of frictional engagement elements that are arranged between the power source and the drive wheels and can change the torque capacity by supplying hydraulic pressure, and an engaged state or a released state with respect to each of the frictional engagement elements A control unit for controlling the supply of the hydraulic pressure to change to a control device for an automatic transmission,
The control unit generates torque capacity and transmits torque to the drive wheels when a start condition among the plurality of friction engagement elements is satisfied when rotation of the drive wheels is zero. The first frictional engagement element is caused by changing a frictional engagement element other than the first frictional engagement element to a released state and then changing the first frictional engagement element from the engaged state to the released state. A learning unit that learns a torque transmission start point of the first friction engagement element based on a difference rotation between the input side and the output side or a change of a rotation element that changes according to the difference rotation;
The learning unit is configured to place the first friction engagement element in an engaged state when the learning is being performed and the start condition is satisfied, and a second other than the first friction engagement element. A control apparatus for an automatic transmission, wherein the frictional engagement element is gradually changed to an engaged state to increase the drive torque transmitted to the drive wheel.

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